Wireless networks, and in particular networks based on the IEEE 802.11 standards, have experienced explosive growth in the last decade. Examples of WLAN usage include Internet protocol (IP) access to a broadband network, streaming applications over IP, (e.g., voice over IP (VoIP), video, etc.), interactive local applications (distributed gaming), localized mesh network with limited or no extra-network access, and machine-to-machine communication such as home and small enterprise automation, sensor network to data network interaction, or distributed computation.
Today, a significant number of organizations rely on wireless networks for their operations. But the wireless communication medium is different from wired communication medium. While the design of wireless local area networks (WLANs), in particular 802.11 WLANs, has done an excellent job at addressing the challenges and opportunities associated with wireless, the same cannot be said for security and robustness of these networks.
The current WLAN security is essentially based on the security of wired networks, which is insufficient and inappropriate for the wireless medium. The most important reason for this is the fact that the wireless medium is intrinsically a broadcast medium. In order for an adversary to overhear communications in the wired network, a physical connection to the wire is required. This means that the first line of defense from eavesdropping in wired networks is physically preventing access to the networks, (e.g., ensuring that adversaries cannot enter a building or that they cannot tap a wire). In contrast, for wireless networks, adversaries can easily witness anything that is transmitted as long as they are within radio range of the transmitter.
Further complicating matters for wireless systems is the ubiquity and portability of the platform itself. The broadcast nature of the wireless medium implies that users are not tethered and that they may access network services from anywhere at anytime, and does not require an access to the wireless network from within a company's building.
In spite of the unique challenges that the wireless domain presents, the approach that is commonly taken to secure wireless networks has been to translate traditional cryptographic network security protocols to the wireless domain. Although the application of conventional cryptographic protocols to wireless networks is essential, such an approach is also incomplete as it completely leaves out the wireless aspect of the problem.
As an example, consider a rather simple selective blocking attack with the goal of severely reducing network throughput. Such an attack is remarkably simple to accomplish in modern wireless networks. To attack an 802.11 network, for example, it is sufficient to modify the carrier sense multiple access/collision avoidance (CSMA/CA) protocol to break the standard-defined rules and create interference specifically when it detects activity in the carrier. Since an 802.11 medium access control (MAC) only sees error corrected packets, it cannot tell the difference between such an attack and a poor channel condition or congestion that results in a packet loss. The MAC layer will therefore back-off subsequent transmission, further lowering its throughput, (i.e., it will do exactly what the attacker wants it to do).
Physical layer security is a scheme of using information obtained at the physical layer for implementing security-related functions. The physical layer security cannot be enabled in the conventional wireless systems, such as 802.xx WLANs, because the measurements required for physical layer security are not made or the measurements are made at the physical layer but not reported to the MAC layer or higher layers, required messaging support does not exist, required flexibility of operation does not exist, or required flexibility of operation exists but is not reported, and the like.
Therefore, it would be desirable to provide a WLAN system and method that enables the support various physical layer security techniques.